#
# Epage 137
#
# Written by:
# -- 
# John L. Weatherwax                2009-04-21
# 
# email: wax@alum.mit.edu
# 
# Please send comments and especially bug reports to the
# above email address.
# 
#-----

# version$language == "R" for R version$language == NULL for SPlus

if(is.null(version$language) == FALSE){ 
  require(alr3)
}else{
  library(alr3)
}

data(BGSall)
attach(BGSall)

# create a factor based on sex:
D = factor( BGSall$Sex, ordered=FALSE )

# fit the two models of interest:
#
m0 <- lm(HT18 ~ HT2 + HT9 + D                , na.action=na.omit)  # this is the null hypotheis 
m1 <- lm(HT18 ~ HT2 + HT9 + D + D:HT2 + D:HT9, na.action=na.omit)  # this is the alternative hypothsis 

anova(m0,m1)